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Algae control in salt water tanks

There is no holy grail for algae control in our aquariums. Algae needs three things to live; water, light and food. To control unwanted algae we must remove one of the three elements. Since we are keeping aquatic life forms it is probably not a good idea to remove the water. Since algae control is primarily of interest to reef aquarists, it would not behoove us to remove light. So that leaves food.

What is food for algae? The primary food for algae is CO2. Chlorophyll in the algae uses energy from the light source to convert CO2 into a simple sugar, such as glucose, that in a nutshell is photosynthesis. Algae also benefit from other nutrients common to our aquariums as well; phosphate, nitrate, silicate and sulfate are the top four. There are many ways to import these foods into our aquaria, use of tap water for top off and water changes. Overfeeding, use of substrate and rock high in phosphate or silicate content.

Whatever the source, we must attempt to limit the nutrients from our systems. This can be accomplished through the use of RO/DI water for top off and water changes, use of kalkwasser also known as “lime water” for top off (precipitates phosphates), use of protein skimmer to remove dissolved organic compounds. Employment of a deep sand bed to remove nitrates, the fauna in the sand will eat the detritus that settles on the sand bed. The anoxic areas of the sand bed will consume nitrates converting them to nitrogen.

The use of animals to remove the food as well as algae itself is recommended. Herbivorous fish such as tangs have an indispensable place in our reefs, as well as grazing snails (astrea, nassarius {not a grazing snail, but benificial} and trochus) and chitons. Small hermit crabs can also be used to scavenge uneaten food.

Aquascaping is also important in algae control, as well as water flow. A tight wall of rock up the back of the aquarium will create dead areas of water flow allowing detritus to settle and become a sight for algae growth. A loose arrangement with good water flow around, under, behind and in front of the rocks will serve our purposes much better. This also has the benefit of requiring less rock = less money. We should strive for water flow that intricate and moves great volumes of water. This will keep detritus in suspension to be eaten by our corals and scavengers or removed to the protein skimmer for manual removal. Here are the specific types of algae and some things that can be done to eradicate it if it blooms.

Cyanobacteria (red slime algae)

Cyanobacteria are really photosynthetic bacteria. Typically it is deep red in color, but is also found in green and blue-green. It forms slimy sheets on aquarium surfaces, rocks and substrates. Cyanobacter will also trap air bubbles under the sheet. This algae is caused by excess nutrients in the system. Treatment is problematic at times; some will recommend the use of antibiotics. This will work, but does not address the underlying problem, the excess nutrients. Siphon out as much as possible; perform a water changes using RO/DI water, increase protein skimming, cut back on the amount of food or the frequency of feedings and use a fresh saturated solution of kalkwasser for top off.

Diatoms (dusty, rust colored)

Diatoms are probably the most common form of algae found in aquariums. Every new aquarist finds diatoms in their tank at the end of their cycle. Diatoms are easily controlled through the use of grazing snails. If you find a bloom check out you silicates, as they are incorporated into this algae’s shell. These algae can also be hindered through the use of RO/DI water for make up water.

Hair Algae

Hair algae are very common pest algae in reef aquaria. The most common cause of hair algae is phosphates and nitrates. (Note: if you use a municipal water supply, phosphate is added to your water by federal mandate, to combat lead piping in old houses) Removal of hair algae can be difficult and time consuming. First; manually remove as much as possible, water change with RO/DI water, reduce the import of phosphates into your system. If you are using a trickle filter or other conventional biological filtration, remove the media. Reduce mechanical filtration, increase protein skimming and maintain high alkalinity. Use herbivorous fish such as the yellow tang to eat the unwanted algae. If it is persistent a reduced photoperiod may be in order.

Dinoflagellates (brown slime, snot algae)

Dinoflagellates are closely related to the endosymbiotic algae in our inverts; zooxanthellae. It is called snot algae because it has the consistency of nasal mucus; it is transparent to brown in color. It lays down stringy sheets, similar to Cyanobacteria, which trap air bubbles in their tissue. This is a very dangerous alga because it has the ability to quickly remove oxygen from your system. It has also been hypothesized that the algae is toxic to herbivorous fish and snails. The treatment is much the same as Cyanobacteria, with an addition, try to keep you ph elevated above 8.6 during the day and above 8.3 at night and you should see it crash pretty quickly. One good thing about this alga is that it is pretty rare.

Valonia spp.

The dreaded bubble algae. These algae have fascinated and frustrated reef aquarists for many years. The real problem with them is they are so darn pretty. If not allowed to over run the tank they can be very interesting indeed. Removal is recommended as soon as they are noticed in the tank, they have the ability to spread very rapidly and encroach on our sessile invertebrates. Removal is simple; use forceps or needle nose pliers and pull them off, preferably without bursting them.